Automatic positioning system having tape responsive servo means



Jan. 19, 1965 T. w. THOMPSON ETAL 3,165,952

AUTOMATIC POSITIONING SYSTEM HAVING TAPE RESPONSIVE SERVO MEANS PHASEDETECTOR Thomds W. Thompson Richard E. Sipfle Frederick L. Fullum, Jr

Robert L. Maynard INVENTORS gi /mam ATTORNEY Jan. 19, 1965 T. w.THOMPSON ETAL 3,165,952

AUTOMATIC POSITIONING SYSTEM HAVING TAPE RESPONSIVE SERVO MEANS FiledJan. 6, 1961 2 Sheets-Sheet 2 e /70 SER PP iASE AMPLIFIER DETECTOR PUNCH'41; l UNIT 4 CONTROLLER ATTORNEY v sirable.

United States Patent Ofifice Patented Jan. 19., 1965 AUTOMATICPOSITIONING SYSTEM HAVING TAPE RESPONSIVE SERVO MEANS Thomas W.Thompson, Nashua, N.H., Richard E. Sipfie, Hamden, Conn, and FrederickL. Fullarn, Jr., and Robert L. Maynard, Nashua, N.H., assignors toSanders Associates, Inc., Nashua, N.H., a corporation of Delaware FiledJan. 6, 1961, Ser. No. 81,063 9 Claims. (Cl. 33-71) by means of rivetsor bolts. The holes are most readily I formed by means of punch presses,which are located at the installations where the beams are cut to sizeand trimmed and otherwise prepared for erection at the cons'tructionsite. The weight of a steel beam of even moderate length is sufiicientto make machine-aided positioning of the beam' with respect to thepunchpress very de- In turn, the use of such machinery militates towardautomatic control thereof to obtain the various punch locations. Anotherimportant factor is the time and difficulty involved inmaking handmeasurements on beamsof moderate or greater length.

Accordingly, it is a principal objectof our invention to provide anautomatic machine tool capable of perform- 1 ing operations atsuccessive points along an elongated work piece of considerable length.

A more specific object of the invention is to provide apparatus forautomatically punching'holes in steel beams at various predeterminedpositions therealong.

- A further object of the invention is to provide appara tus of theabove type which accurately locates the holes to'be punched. 7

Yet another object is to provide. apparatus of the above type which iswelladapted to punch holes at diflfer'ent lo-: cations onsuocessive'beams.

A still further object of the invention is to provide a machine tool ofthe above type which i's'relatively simple in design yet reliable andaccurate in operation.

Other objects of our invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the features of construction,combination of element, and arrangement of parts which "will be'exemplified in the construction hereinafter set forth and the scopeo'f'the invention will be indicated in the claims.

- In general, our' invention uses a servo controlled bydraulic. motor toposition beams in the proper location beneath a punch'press; Theelectric-hydraulic servosystem operates in response to signals developedfrom .in-

structions programmed in digital form on data storage devices such aspunched cards. The use of such cards facilitates'vari-ationof thepunching instructions for different'. beam.

The beam to bepunched rides on rollers which support its weight andminimize frictional forces during move-' ment; It is pulled or: pushedover the rollers, as the case may be, by a carriage supported on railsand driven therealong' by the servomotor.

The servomotor operates: through a;pinion meshing with a rack afiixed tothe carriage' Af'feedback transducer providesa signal indicative oftheposi'tion of the carriage and the beam attached 7 thereto, by meansof a. second pinion connected to the rack and rotated in-i-accordancewith its movement. The.

output of the transducer is used to provide a conventional error signalfor the servosystem. v

The system is relatively simple in design and yet it positions the beamswith a high degree of accuracy. Furthermore, its simplicity, togetherwith the inherent ruggedness of the positioning mechanism, provides ahigh degree of reliability. Reliability is enhanced by a novel nulldetector which determines when the beam has finally come to rest in thecorrect location and emits a signal initiat-L ing the punchingoperation. Another advantage of our system is the fact that it isreadily used with existing beam-punching equipment.

For a fuller understanding of the nature and objects. of invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings, in which:

FIGURE 1 is, a schematic representation of a beam punching systemincorporating the principles of our invention and includes a simplifiedperspective view of the punch press and associated mechanical elements,and FIGURE 2 is a schematic diagram of the null detector used toinitiate the punching cycle.

As seen in FIGURE 1, a carriage generally indicated at 10 moves a beam12 over rollers 14 to position the beam-beneath a stationary punch unitgenerally indicated at 16. The carriage 10 is powered by ahydraulic'servo motor '18 acting through a pinion 20 which meshes with arack 22 attached to the carriage. The motor 18 is controlled by aservosystem in accordance with instructions recorded on punched cards 24fed to a card reader 26.

More specifically, the carriage 10 rides over-a pair of rails 28 bymeans of wheels 39 journalled in columns 32.

which engage the beam 12, and a reference pin 46 extend ing through andin slidable engagement with the arms 42 and 44. The end of the beam 12within the gripper 38 bottoms against thepin 46, thereby providing afixed correspondence of points along the beam with points along the rack22. Stillreferring to FIGURE 1, an end 22a of rack is supported by aroller support not shown.

The output of the card reader 26 is converted to an analog signal by adigital-to-analog converter 56. The

the rack 22 is suitably secured to the housing '36 and the output of theconverter 56 is one of the inputs of a summing unit 58. The other inputof the summing unit is taken from a position sensor, generally indicatedat 60,

"coupled to" the rack 22 by a pinion 62 keyed toia shaft 6.49 The sensor60 may be 'a conventional device providing an" electrical output signalindic ative of the number of pinion turns and fractions there of from azero or reference angle. Thus, the transducer output signal correspondsto the position of the rack 22, which rotates'the pinion 62 as it movestogether with the beam 12.

. Preferably, sensor 60 is of the autotransformer t pe which a pluralityof taps on an autotransformer are selectively switched, as thefpinion 62rotates, .to varyinidiscrete steps the output voltage ofthe transformer..A potentiometer may also be included for interpolation be tween thevoltage increments. .The converter 56 may be a similar unit, withconnections tothe taps of autotransformers made by relays actuated inaccordance with holes in the punched card 24. vPreferably, the converter56 and sensor 60 are both excited by an alternating currentlpower source66. Therefore, the ratio of the output voltages of the converterandtransducer is independent of the outputvoltage of the sourceod and, moreimportannwhenthe. actual positionof the beam 12,-as indicated by thevoltage from the sensor so, is-equal to the desired positionsas error.

controlling the fluid flow from a hydraulic pump 74 to the indicated bythe output oi the converter d, the two voltages will be equal regardlessof variations in power supply 1 magnitude is proportional to thepositional error vof the bea'm'12 and whose polarity indicates thedirection ofthe This sig'nalis used to operate a servo valve 72hydraulic motor 18. The direction offluid flow to the motor. 18 iscontrolled by the servo valve 72 such as to reduce the positional errorof the beam 12 and thus to move it to the desired position recorded onthe card 24.]

- The output of the amplifier 63 is also applied to a null detector 76,to be described in detail, which emits a signal to, a punch unitcontroller 78 when the beam 12 has come to rest in the desired position.In accordance with the instructions on the card 24, the controller 78determines which of several punches (not shown) in the unit 16, arrangedacross the beam 12, are to be operated at the various punch locationsreached by means of the above positioning system. Thus, variouscombinations. of holes at the different locationsmay be obtained, asshown by the'holes 80 of FIGURE 1. Each punching operation is initiatedby thesignal from the null detector7o. Preferably,,the punch unit 16also includes means (not shown),

' for sensing completion of the punching operation and transmitting asignal to tliecontrollerfih, which retracts v the punches and, in turn,emits a signal to the card reader 26. The card reader thereupon advancesthe card 24 to read the next set of punching instructions, i.e., thelongitudinal and transverse location of the next set of holes 563 in thebeam 12.

I n-many servo positioning systems, an indication that a desiredposition has been finally reached may be taken directly from" the outputof the servo amplifier, since the I detectorincludes a full wave.rectifiercomprising diodes r 82 and 84' connected to rectify the outputof the amplifier 6 8. The diodes are connectedto one end of apotentiometer 86, the otherend of which is returned to ground resultingemitter-collector conduction through the relay 'coil 94a. The relaycontacts 94b, Q40 are closed by the energized coil to initiate thepunching operation.

As is always the case in automatic positioning systems, the systemdescribed above generally does not bring the. beam to rest in exactlythe desired location. Thus, when the beam comes to rest, there isgenerally a small error signal which is insutiicient to cause operationof the hydraulic motor 18, but which does appear at the output oftherectifier contained in the detector 76. Thus, if the tap so. werepositioned at thetop of the potentiometer 8d, its potential and that ofthe transistor base 9% would almost always remain positive, even withthebeam 12 in position for the punching operation, and, therefore, the

latter operation would not be initiated by the null detector.Accordingly, the tap 86a is positioned down on the potentiometer asuficient distance to obtain a negative voltage whenever the errorsignal obtained with the beam 12 at rest drops below the levelcorresponding to the maximum final positional error to be expected.

The capacitor 93 serves two functions. It insures stop page of the beam12 in the desired location before the punching operation begins and italso prevents damage from beam to beam. As a result, some beams mayovershoot their final positiom i.e., pass through from one direction andthen return frorn the other direction. In othercases, the beams maycoast from the position cor responding to the setting of thepotentiometer tap-86a to a position corresponding to a considerablysmaller error voltage. In either of these cases, if the detector. 76emits a signal when the error voltage first dropsbelow the levelcorresponding'to the potentiometer setting, the punch unit 16 will beactuated before the beam 12 comes to rest, with resulting damage to thepunch unit.

As the beam 12 moves to a new punch location, the

amplified error signal diminishes continuously untilthe.

desired position of the beam is reached. The voltage across the'capacitor 98 moves toward a valve level corresponding: to the errorvoltage. tends toward the difference between the voltage of thebatteryatiti and the rectified error voltage, multiplied by the. ratioof the resistance between the tap 86a and the junction 96 to the entireresistanceof the potentiometer.

, 86. Becauseof .thetime constant involved in charging the capacitor,its. voltage lagsbehind the level correthroughabattery 88, whosepolarity is opposite to that of therectifier: Themovable tap 86a of thepotentiometer 86 isconnected to the base 9th: ofa p-n-p transistor il byway-{of current limiting resistor 92. ,The coil 94a of a :relaygenerally indicated at 94 is connected between the collector 90b of thetransistor 9d and the junction-Jot the potentiometer 86 and battery 88;Theernitter Qilc of the transistor is connected to the other terminal ofthe battery,

Le, ground. The relay94 also includes normally open contacts94hand94c,which arejclosed when the coilfida.

is energized-to complete a vcircuit in the controller 78 and tivevoltage appears at the output of the full wave rectifier sponding totheerror voltage. In'particular, as the beam approaches its finalposition," the capacitor voltag'eL-is somewhat greaterthanthezcorresponding level, although both are, of course, decreasing.

' Thus, when the errorvoltage drops to a point atwhich .thecorresponding voltage level is such as't'o permit con 1 duction in thetransistor Qt} to initiate operationof'the, punch unit, the actualvoltage atthe tap 86a is greater.

Conduction" in the transistor is therefore delayed-ifor' alength oftirnedetermined byfthe,

than this" valve.

time'constant of the capacitor 98-,and associated discharge pathsthrough' the potentiometer S 6. .The position of the tap 86a along thepotentiometer 8fiildeter determining the delay betweenthe time thislevel is atdiodes 82'and- 84. Assuming the proper setting of the Vpositive potentiahand, with this potential applied to the base9tla, thetransistor J ll will be cutoff and relay coil 94a is not energized. Whenthe beam llfilcomes to rest ma punch location, the voltagefrom therectifier drops; "and'- the tapstia moves to a negative:.potential. Thisauses base-emitter cbnduction in: transistor Qtiewith:

tap' 86a, as set forth below, the tap will also beat a J tained andconduction actually begins. "The tap 86a is set so that transistorconduction will notstartfuntil the: beam comes to rest. f v

valve required to provide a power output from the motor 18 (FIGURE l)and the beam :12 moves toward its,

final position, the holding action of the capacitof'98pre u ventsconduction inthetransistor 99,.thus delaying punch) i unit, operationuntil the beam is actually'atjresh Inf.

More particularly, it

In other words, when the error signal drops below cases where there isovershoot, the error signal rises above the valve corresponding totransistor 90 conduction and thus prevents further discharge of, thecapacitor 98. Then, as the beam 12 reverses direction'and returns towardits rest position, the capacitor again discharges to provide delayedtransistor conduction in the manner described. 1

Should the servo amplifier 68 failjthe power to the motor'18'will becut'oif and the beam 12 will' come to a stop. 'Atthe same time, therectifiederror: signal applied to the potentiometer 86 will drop toinitiate the punch operation "although'the beam is not in the correctposition. Here the delay imposed by the capacitor 98 again will permitthe beam to come to rest before being punched, thereby preventing damageto the punch unit 16. However, the chance of the servo amplifier failingbefore that of the power supply is so remote as to be negligible.Internal fusing is more apt to'open circuit the power supply. In theevent of power supply failure, even though amplifier 68 is stilloperable it is without power, the contacts of relay 9.4 will not closeand the punch unit 16 therefore will not be actuated.

It will thus be seen that the objects set forth above, among thosemadeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

It is also to be understood that the following claims" are intended tocover all of the generic and specific features of the invention hereindescribed, and all state ments of the scope of the invention which, as amatter of language, might be said to fall therebetween.

What is claimed is: i

1. Apparatus for punching an elongated member, said apparatuscomprising, in combination: ways along which a punch unit extendingacross said ways and adapted to punch said member, means on saidcarriage for gripping an end of said member, program means for settingup punching instructionsin digital form, said program means electricallyconnected to a servosystem, said servosystem traversing said carriagealong said guide to position said member along said ways in'responseto'said instructions, detecting means emitting a signal when said memberhas finally come to rest in a position in accordance with saidinstructions, means for initiating operation of said punch unit inresponse to said signal, said detecting means including switching meanshaving a pair of control terminals and operable at -a given potentialbetween said directional voltage which is a function of the magnitude ofthe positional error of said member, and an integrating circuit couplingsaid voltageto said terminals so as to delay the appearance of saidpotential at said control 7 terminals until said member has finally cometo rest.

2. The combination defined in claim 1 in which said detecting meansincludes means generating a unidirectional voltage between a firstterminal and a common reference point, said voltage being a function ofthe magvoltage divider, switching means having control terminalsconnected between said tap and said common point" f and integratingmeans arranged to make changes-in the T voltage between said controlterminals'lag changes in 1- said positional error.

3. The combination defined in claim 1 including means for generating avoltage corresponding to the position of said member indicated bysaidinstructions, means for developing avoltage corresponding .to the actualposition of said member, means comparing said voltages to provide anerror signal, and a motor connected to traverse said carriage inresponse .to said error signaL. 4. Apparatus for punching an elongatedmember, said apparatus comprising, in combination, ways along which,

said member travels, a pair of rails extending along said ways onopposite sides thereof, a carriage ridingon said rails, a punch unitextending across said ways, said punch unit having punches adapted toform in said member a plurality of holes disposed transversely withrespect to each other on said member, a gripper carried by said carriagefor gripping an end of said member,-

said gripper having a reference surface abutted by said end to locatesaid end with respect to said carriage, a recording medium carryingpunching instructions in digital form, said instructions including thelocations of holes along said member and the designation of which ofsaid punches are to be actuated at each of said locations,

means for reading said digital instructions, means for generating afirst voltage corresponding to said locations .along said member,sensing means providing a second voltage corresponding to the positionof said member along said Ways, means for comparing said first andsecond voltages to derive a positional error voltage, means foramplifying said error voltage, a hydraulic motor coupled to saidcarriage to move it along said rails, a valve controlling the flow offluid to said motor in accordance with the amplified error signal,actuating means controlling the punches in said punch unit in'accordancewith said instructions, and means responsive to said error sig nal forinitiating operation of said actuating means when said signal hasdecreased below the value corresponding to the maximum positional errorof the system for a sufficient time to insure that said member has cometo rest in a position in accordance with said instructions.

5. The combination defined in claim 4 including a rack I connected tosaid carriage and extending parallel to the direction of travelthereof,said hydraulic motor having a first pinion meshing with said rackto-drive said carriage, said sensing means including a second pinionmeshing with said rack and means for generating a .voltage which is afunction of the angular position of said second pinion.

control terminals corresponding to the maximum positional error of saidservosystem, means generating a un1- 6. The combination defined in claim5 in which said initiating means includes switching means having a pairof control terminals and operable at a given potential between saidcontrol terminals, means generating a unidirectional voltage which is afunction of the magnitude of said error signal, and an integratingcircuit couplmg said voltage to said terminal.

7. The combination defined in claim 5 in which said recording medium isa punched card, each row of holes on said card containing a set ofinstructions for the punch ing of holes at a location along said memberand including means for indexing said card to the next set ofinstructions upon completion of each punching operation.

8. A servo-positioning system comprising, in. combination, meansgenerating a voltage corresponding to the-desired position of an object,sensing means generating a voltage corresponding to the actual positionof said object, means for comparing said voltages to. provide anerrorvoltage, means for amplifying said error voltage, drive means for movingsaid object in response to the amplified error voltage in such manner asto dicluding means developing a unidirectional voltage between r a firstterminal and a common reference point, said uni directional voltagebeing a function of the magnitude of said error voltage, aunidirectional voltage 'sourcefconnected between a second terminal andsaid commonfpoint,

a voltage divider connected between said first and second r v 4terminals, the polarity jof said first terminal with re spectto acornmonipoint' being opposite to that of said second tefminal withrespect to said common point, said voltage dividerhaving atap, switchingmeans ,having a control terminal connected betweensaid common point and:said tap,rand delaymeans arranged to make the changes in thevoltagefbe'tween said control terminals lag the"changes in said errorsignal.

' '9: The combination defined in'clairn 8 in which said switching meansinclndes a transistor having an emitter, a" base and a collector, anormally open relay having I a coi1"'conn'ected in series withsaidvoltage source between said emitter and said co11ector,-rneansconnecting said base to said tap, and a capacitor connectedbetween 1,650,748 7 Thomas Nov, .29, 1927 2,866,506 Hierath et a1 m; ec.30, 1958 2,886;755 Ehretet a1. May 12, 1959 V Horton Apr. 18, 1961UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N003,165,952 January 19, 1965 Thomas W, Thompson et al.,

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 4, lines 42, 58 and 71, and column 5, line 2, for "valve", eachoccurrence, read value Signed and sealed this 24th day of May 1966.

\ttest:

RNEST W. swmER EDWARD J. BRENNER 'Testing Officer Commissioner ofPatents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No3,165,952 v January 19, 1965 Thomas W, Thompson et al,

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 4, lines 42, 58 and 71, and column 5, line 2, for "valve", eachoccurrence, read value Signed and sealed this 24th day of May 1966.

\tteSt:

rtesting Officer Commissioner of Patents :RNEST w. SWIDER EDWARD J.BRENNER-

1. APPARATUS FOR PUNCHING AN ELONGATED MEMBER, SAID APPARATUSCOMPRISING, IN COMBINATION: WAYS ALONG WHICH SAID MEMBER TRAVELS, AGUIDE EXTENDING ALONG SAID WAYS A CARRIAGE ENGAGING SAID GUIDE FORMOVEMENT THEREALONG, A PUNCH UNIT EXTENDING ACROSS SAID WAYS AND ADAPTEDTO PUNCH SAID MEMBER, MEANS ON SAID CARRAGE FOR GRIPPING AN END OF SAIDMEMBER, PROGRAM MEANS FOR SETTING UP PUNCHING INSTRUCTIONS UN DIGITALFORM, SAID PROGRAM MEANS ELECTRICALLY CONNECTED TO SERVOSYSTEM, SAIDSERVOSYSTEM TRAVERSING SAID CARRIAGE ALONG SAID GUIDE TO POSITION SAIDMEMBER ALONG SAID WAYS IN RESPONSE TO SAID INSTRUCTIONS, DETECTING MEANSEMITTING A SIGNAL WHEN SAID MEMBER HAS FINALLY CONE TO REST IN APOSITION IN ACCORDANCE WITH SAID INSTRUCTIONS, MEANS INITIATINGOPERATION OF SAID PUNCH UNIT IN RESPONSE TO SAID SIGNAL, SAID DETECTINGMEANS